Modern wireless communication systems with large bandwidth and high peak-to-average power ratios (PAPRs) have been and will continue to be in high demand. This puts a strain on the transmitter, which has to operate with its average power in the output back-off (OBO) region. The Doherty power amplifier (Doherty PA) was invented in 1936 as an alternative to the highly inefficient linear amplifiers used in radio transmitters. The Doherty PA has recently undergone a renaissance, becoming the PA architecture of choice for mobile radio base stations. The additional efficiency peak at the OBO point makes it ideal for high PAPR signals. However, the main drawback of conventional Doherty PAs is its narrow bandwidth, which significantly limits its applicability. Recently, broadband Doherty PAs have been realized using a technique called “post-matching” and have attracted much attention. In this paper, the operating principles of conventional and broadband Doherty PAs are reviewed, followed by an analysis of recently reported prototypes, current technical challenges, and application in 5G wireless communication systems. As a comparison, process technologies for the implementation of Doherty PAs are also surveyed.
In-Band Full-Duplex is a powerful technique which theoretically doubles the spectral efficiency. It significantly contributes to the ever-increasing demand for high data rate and good connectivity of future communication systems. Self-Interference from the transceiver is the most challenging issue in In-Band Full-Duplex system implementation. In the presence of transmitter power amplifier non-linearity and phase noise in local oscillator, cancellation of the self-interference becomes more complex. In this paper, a detailed comparative study of two major Digital Self-Interference Cancellation techniques namely, Least Squares method based Dynamic Regression for Nonlinear Digital Self-Interference Cancellation and Least Mean Squares based Adaptive Nonlinear Digital Self Interference Cancellation is done. The study of the algorithms is done with Orthogonal Frequency Division Multiplexing that uses a bit-interleaved coded modulation system. The performance of the algorithms is studied in terms of bit error rate, convergence time and computation complexity in the presence of time varying fading channel with power amplifier non-linearity and phase noise.
Operational amplifier has two differential amplifier stages followed by a buffer transistor(for high i/p impedance) and finally output stage(emitter follower for low o/p impedance).
We report high-energy, high-efficiency second harmonic generation in a near-infrared all-solid-state burst-mode picosecond laser at a repetition rate of 1 kHz with four pulses per burst using a type-I noncritical phase-matching lithium triborate crystal. The pulses in each burst have the same time delay ( ${\sim}1~\text{ns}$ ), the same pulse duration ( ${\sim}100~\text{ps}$ ) and different relative amplitudes that can be adjusted separately. A mode-locked beam from a semiconductor saturable absorber mirror is pulse-stretched, split into seed pulses and injected into a Nd:YAG regenerative amplifier. After the beam is reshaped by aspheric lenses, a two-stage master oscillator power amplifier and 4f imaging systems are applied to obtain a high power of ${\sim}100~\text{W}$ . The 532 nm green laser has a maximum conversion efficiency of 68%, an average power of up to 50 W and a beam quality factor $M^{2}$ of 3.5.
If you buy a “WiFi signal booster”, what you’re probably going to get is a Wireless repeater
. It will contain at least one (fairly modest) RF power amplifier, but that will be only a small part of it. It’s a complicated, mostly digital device that has much of the same componentry as a wireless router. It listens for packets of data on the network you set it to boost, and then rebroadcasts them. It’s a
Aiming at correcting the error caused by the nonlinear and power supply noise of the bridge-tied-load (BTL) power stage of the filterless digital class D power amplifier, an error correction method was proposed based on feedforward power supply noise suppression (FFPSNS) and first-order closed loop negative feedback (FCLNF) techniques. This method constructed the first-order LCLNF loop for the power stage and further reduced the impact of the power supply noise on the power amplifier output by using FFPSNS technology to introduce the power supply noise into the feedback loop at the same time. The 0.35 μm CMOS process is used for analysis and comparison in Cadence. Cadence simulation results indicate that PSRR at the power supply noise frequency of 200 Hz is improved with 36.02 dB. The power supply induced intermodulation distortion (PS-IMD) components are decreased by approximately 15.57 dB and the signal-to-noise ratio (SNR) of the power amplifier is increased by 17 dB. The total harmonic distortion + noise (THD + N) of the power amplifier is reduced to 0.02% by FCLNF + FFPSNS.
Traditional earphones and speakers need to use audio cables to connect mobile devices and sounding units when using audio files of mobile devices such as mobile phones as audio input sources. This paper proposes a solution to this problem. This paper studies and designs a power headphone amplifier integrated system based on Bluetooth technology with STM32F407 as the main control core. The system uses CSR8670 Bluetooth audio SoC chip to realize Bluetooth audio transmission, uses TPA6112 headphone audio amplifier to realize amp function, uses HT8696 class D power amplifier to realize speaker power amplifier function, uses 3.2 inch resistive touch screen to realize human-computer interaction function, and the system introduces STemWin graphics library Implement human-machine UI interface. The system is more practical in the independent output of the amp and the speaker power amplifier circuit, the control method is more humanized, and the human-machine experience is better, which plays a driving role for the popularization of the smart home.
Usually CB stages (or common gate (CG) stages, when FETs are used in the amplifiers) are an essential part of RF amplifiers. In combination with a common emitter (CE) stage they build what is called a cascode stage which displays (approximately) the good properties of the CE stage while overcoming its major shortcoming: the poor bandwidth due to Miller effect. Below is the raw picture of the stage, in BJT and CMOS versions, with the biasing circuitry omitted.
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